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Slipping Clutch.


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I just took my 71 240Z for its first test run after doing an auto to manual tranny swap. Its a 5 speed out of a 78 Z. The push rod on the slave cylinder was too long, and was keeping me from being able to mount it without engaging the fork a little, so I cut about 1/4" off the rod so I could attach it without resistance. Taking off in 1st seems fine, but then as I get into 3rd, 4th, and 5th it slips when I punch the throttle. So I chopped another 1/4" off and it's like it just keeps self adjusting and wont let the clutch fully engage. The clutch and pressure was bought from a guy some time back who said these would work fine for my  tranny setup. They were new. Could I have the wrong setup here, or is there an adjustment procedure I need to do? 

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One common place to get tripped up is the throwout bearing collar. There are several different length collars and the length must match the presure plate you use. If the collar is too long it can hold the clutch in a partially released position. conversely, if hte collar is short the clutch will not fully release when you press the pedal down. to check this you must remove the engine and/or transmission.

 

When the clutch is engaged (foot off the pedal), is there a lot of force on the push rod at the slave cylinder? Can you press the slave piston back into the bore at all?

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If it's a 240Z clutch, use the collar for the 240z. If it's a 280Z clutch, use the collar for that clutch. Throw out bearings are the same. If you don't match the collar to the clutch, you'll be screwing with it forever. You can choose either clutch and collar for the 5 speed but collar and clutch have to match. I always match the arm lever too......240z arm to 240Z clutch and 280Z arm to 280Z clutch.

Edited by Diseazd
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Here's another - http://www.classiczcars.com/topic/44389-l28-is-toasting-my-240z-clutch/page-2

 

92-95 mm from the fork surface of the collar to the flywheel surface is the key.  That puts the end of the fork in the right spot for the slave cylinder and its rod.

 

By the way, when Diseazd says "clutch" I think that he's talking about the whole assembly of pressure plate aka "cover" and clutch disc.  The pressure plate and its cover come in different heights, that need different throwout bearing collars.

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I think I have the wrong collar. I remember when I was mating the trans to the engine that no matter how hard I tried I couldn't get it to slide together the last 1/8 to 1/4 inch or so. So, I did what you should never do. I ran the bolts in and pulled it together that way. And I'll just bet that the throw out bearing is keeping just enough pressure on the clutch fingers when my foot is off the clutch, causing the slight slippage at higher rpm's. 

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It's happened before.  You probably got the collar and bearing with the transmission and the pressure plate and disc separately, right?  Bummer.  Hopefully the parts didn't take too much heat.

 

Some clutch kits come with a collar included so there's no mismatch possible.  

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Beermanpete..... Yes, there is alot of pressure. I can't move it at all. The fork has no play at all either. I think I'll be pulling the trans tomorrow. I can assume I'll need a shorter collar, but how do I figure out which shorter one, and I already checked out my local parts suppliers, and they only offer the bearings. I guess It's another week to wait on parts.

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Yes ZED, it was a hodge podge of parts that I figured I'd roll the dice on. I knew something like this was bound to happen. On a positive note, the transmission shifts through all 5 gears flawlessly and reverse works!

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I can get the collar from Oreilly's, but only in the complete clutch kit. It's only a hundred bucks. I just ordered it. It comes in Sunday. I will do the measurements from the link in post 5 before I reassemble it. 

 

Thanks again!

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One last thing - there are two sizes of clutch, 225 and 240mm.  The bolt patterns of the pressure plate assembly are different, and the height.  Do you know which you have?  Some people use the 240 mm for performance applications.  They came stock on 2+2's and the later ZX turbo cars.  The visible difference is that the 240 has 6 evenly spaced mounting holes and the 225 has 3 sets of 2 closely spaced holes.  The factory fywheels only fit one style each.  So if you ordered the clutch for the car model, or the transmission, it could still be wrong.  More to worry about.

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The clutch kit I ordered from Orielly's has a clutch disc diameter of 225.43. But it also comes with the pressure plate as well and the throwout bearing and collar. My plan is to install the whole new kit from Orielly's and discard the crapshoot that I installed earlier. And no, I don't really know what I have. I'm just hoping that the kit from Oreilly's might just fix the problem. But at least I have more info going into it this time.

Edited by glassguy
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I thought you might be able to remember the pattern of the bolts, tightening two that were close together or six evenly spaced.

 

Anyway, you can always return it and start again.  OReillys will usually bring parts in just to look at.  Might be worthwhile to just have them bring both in.  

 

Don't forget to drain the new fluid, for reuse, before taking the trans. back out.  

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It sounds like the collar is too long. It sucks but others have there. I know I have. When you get the new parts, compare them to the existing parts. Hopefully you will get a different length collar or a differnt height pressure plate. Check them for total distance to the flywheel surface as shown in the photo contained in post #35 in the link provided by Zed Head above. When you put the trans bac kon the engine the release arm should be able to move freely a bit before it contacts the collar and TO bearing.

 

Once you are done, Keep the spare collar for the next time you replace the clutch in case you get a different height pressure plate.

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I'm almost positive that the 6 bolt holes on the pressure plate are evenly spaced. Also, the guy I bought these parts from was all about big cams and triple webers on his Z's, so I wouldn't be surprised to find out he sold me the 240mm flywheel. He probably even told me this too, but that was over a year ago and I've forgotten that by now. So, I went ahead and ordered a 2nd clutch kit for a 77 2+2 that lists it as a 241.3mm. Thanks again everyone for the great info and advice! I think I have this one in the bag! I'm off to the garage!

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So here's what I have. The collar in my junkyard 5 speed transmission that came out of a late 280z, not 2+2, has the "type B 4 speed collar" in it. My pressure plate and clutch disc are the smaller correct 225mm or 8 7/8" style. Wish I could just buy the collar, but at least I'll have a spare disc and pressure plate.

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  • 4 months later...

Did you get this workign correctly? When you trimmed off the rod to releive the pressure being held on the plate, did you notice that clutch performed properly for a few strokes? this is where i'm at, sounds the same situation as you. Same transmission swap even.

 

----

 

I recently put a 79 280ZX type B 5 speed in my 240Z. I used the bearing collar and fork that came with this 280ZX transmission. I'll post some pics shortly to compare between the B type 4 speed TOB collar/fork I swapped out. The 280zx fork had an indentation where the clutch slave rod would sit against, vs the 4 speed with an indentation and and hole. I used the clutch slave that was already in the car, (a generic 240Z replacement, size I'm uncertain). This slave has a threaded rod, with adjustable nut on it. In order to use with the new fork, I drilled a hole the same diameter as the piston threaded rod in the fork indentation, allowing the rod to slide through and sit happily.

 

Currently, I believe the TOB to have a slight pre-load against the clutch. I get complete disengagement in the first 1/4 of pedal travel. If I were to dump clutch at 6000 RPM, it would slip rather than spin tires. If I shift aggressively, you can feel it slip a small amount. Engagement under throttle is soft, not firm.

 

Clutch is a cheap eBay KUPP Racing Stage 4 - 6 puck rated at ~400 HP...

 

Flywheel is a 143281 Fidanza aluminum

 

Engine is 3L L28 producing 282HP/272TQ at flywheel.

 

Because it seemed the slave was releasing the clutch far too soon, I crawled under the car and backed off the adjustment nut on the slave cylinder rod to see if the clutch would take up the slack. There was no play and I couldn't move the fork by hand, at all. I backed it off about 3/4" where there was still significant pressure behind held between the fork and slave cylinder. I hoped in the car and pressed the clutch to the floor and released it. The clutch now engaged roughly 1/4 stroke off the floor and felt totally normal. I went for a quick boot and the clutch grabbed VERY hard, and held well in all gears allowing wheel spin in 1st and 2nd. Though after a few clutch depressions the pedal/slave began to release again in the original spot, just barely depressed, and the clutch would again begin to slip.

 

SO.... I believe the TOB collar may actually be the correct length, but instead perhaps the clutch pedal to master needs to be adjusted. I don't know, but it sounds from my reading that the master plunger may not be releasing far enough to allow fluid to return to the reservoir, so a preload is being held against the slave, which may explain how the "slack" i created has been taken up.

 

Am I on the right track? It seems this cheap clutch is holding up fine even after some slipping abuse, as it seems under full release it sticks like glue to that flywheel.

 

 

It sounds like the suggestion here is that the collar is too long, but if that was the case, why would shortening the slave piston length temporarily solve the problem. It seems the slave just ends up enagaging to far. Unless this is NORMAL, in which case then yes I agree the collar is just too long.

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If you measure the distance from the front of the bellhousing to the clutch fork you should read about 110mm for a standard clutch give or take a couple of mm for wear and tolerances. This is on a standarx clutch and aftermarketunit could vary a little.

This will give the slave cylinder about 10mm IIRC. The slave cylinder has a small spring behind the piston to remove slack in the mechanicals. If the collar is too long this piston will be pushed right back hard and the clutch will not release completly. If you can't push the clutch fork into the slave cylinder, then you have a problem.

This could be your problem and shortening the push rod could be enough to solve the problem.

Edit: I see you have an old style slave with push rod. Mist that with all the 280zx stuff.

If you are using the older style it needs an external spring to pull the fork back to the slave cylinder. To adjust it remove the spring. The piston should bottom out by adjusting the fork and them turn the nut 1-1/2 turns back. Replace spring. That will give you the correct free play in this type.

If there is not enough adjustment to do this then you have a problem with mismatched parts.

Edited by EuroDat
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The slave cylinders for the manual adjusting clutches ( with threaded rod, nut and ball nut ) are different from the Auto adjusting ones are different from the from the self adjusting clutches. Install a manual slave or take your self adjusting clutch slave apart and remove the coil spring inside. That will stop the self adjusting feature.

 

You will have to add an external return spring from the clutch fork to the slave cylinder when you use a manual adjust setup. The early manual adjusting fork has a hole for the external spring, and the early slave cylinder has protrusion and a hole for the other end of the spring to slip into. The later style fork an slave cylinder don't have these. You'll have to drill a hole in the fork for the return spring and find somewhere to hook it on at the slave.

 

However, the later self adjusting slave cylinder " should " have worked fine. I believe you are correct in your theory that the Master Cylinder is not returning far enough and this is causing the system to " Pump Up ". This is exactly what will happen if the Master Cylinder ( Clutch or Brake ) does not have enough free play.

 

The FSM has a measurement to setup the MC free play, but here is a quicker and easier way. At the threaded rod connecting the CMC to the pedal loosen the Clevis lock nut and remove the Clevis lock pin. Adjust the Clevis so that you do not have to push the clutch rod in ANY amount to align the clevis hole with the pedal hole. IE: The clevis pin should just slide through with no movement of rod required. Now you are sure that the Master Cylinder is returned all the way. The cylinder has a retaining ring that the piston bottoms against.

 

Adjust your free play at the slave end ( if using manual adjuster ) so that you have 3/16" to 1/4" free play at the fork. This should give you about 1/2" to 3/4" free play at the pedal. 

Edited by Chickenman
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Here's another tip for setting up the Clutch pedal height. The clutch pedal often sits higher than the brake pedal. I don't like this so what I do is shorten the Clutch Master Cylinder pedal rod so that you have to push the pedal towards the Firewall to slip the Clevis pin in place. This is always safe as the piston in the CMC will always be returned Full Stop against the retaining ring.

 

What causes a problem is if the rod is too long and you have to push the CLEVIS towards the firewall to slip the Clevis pin through the pedal hole. Get the rod just " slightly " too long and the Piston seal lip will cover the exhaust port and you get " Pump Up " and a slipping clutch.

 

Edit: The clutch pedal also has a Pedal Stopper on it to adjust pedal height. However, you must remember if you lengthen the Pedal stop rod ( to lower Clutch pedal height ) you must SHORTEN the Clutch Master Cylinder rod length by the appropriate amount. Otherwise you push the piston into the bore and cover the exhaust port. Again causing " pump Up ".

 

Same applies to Brake pedal and Brake Master Cylinder.

Edited by Chickenman
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Fantastic information. I'm working nights this weekend out of town, but I'll run through this a few times before taking a crack at it. Thanks a tonne guys.

I don't have the auto adjusting CSC as the transmission didn't come with one. Working with a manual adjust. I'll grab a small cpil spring on my way back into town.

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i was really surprised how much difference a small adjustment makes at the mc rod - a few turns and you can go from a clutch that won't disengage to one with no free-play at all. do a couple turns, check the clutch travel and function, then do more, check, repeat till you get it where you want it. it means being upside-down under the dash a couple of times, but it's great when the adjustment is correct.

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  • 2 weeks later...

Just took a stab at some of this theory. I'll post my thoughts and have another read through here and elsewhere. I'm feeling my clutch is probably just toasted at this point.

Wanting to rule out the pressure build up theory at the CMC, I adjusted the CMC rod at the pedal to allow full return of the master piston. After doing so, thethe clutch behaved the same and slipped in the same situations. The only difference being more requires pedal depression to achieve release.

I checked the CSC to assure there wasn't any force being applied against the fork and that the fork had the room required to allow a full release. I was able to wiggle the fork at the slave rod with minor effort as well as push the slave piston inward.

This leaves two possibilities (I think)

1. The clutch is just toast.

2. The collar is actually just tall enough to always have some pressure against the pressure plate fingers, when it's bottomed out. (Unlikely)

From L to R. My collection of collars. '70 4 speed B, '73 4 speed A, '79 5 speed B.post-23609-14382126281617_thumb.jpg

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